Ritual Card; Northwestern Yunnan Province, China; 18th-20th century; Ink and paint on paper; 6 x 8 5/8 in. (15 x 22 cm); Collection of Dr. John M. Lundquist

Just as you might own a favorite piece of furniture from your parents’ house, Quentin Roosevelt II (1919-1948), Theodore Roosevelt’s grandson, first encountered the art of the “strange people known as Naxi,” as he later described them, around his family home in Oyster Bay; his father, Theodore Roosevelt Jr., and uncle, Theodore’s brother Kermit, had bought objects as souvenirs during a trip to the Himalayas. The younger Mr. Roosevelt, an art history major at Harvard, liked the stuff, so his family gave him a Naxi scroll for Christmas.

At age 19 Mr. Roosevelt wrote what remains the sole academic dissertation on Naxi art in Western scholarship. He went on to amass the most significant group of Naxi artifacts outside of China. His holdings, mainly those acquired on a 1939 trip through China’s Northwest Yunnan Province, make up this first-ever exhibition of the material.

Chances are you haven’t heard of the Naxi (pronounced NAH-shee), a group of 300,000 people living on the east end of the Himalayas at the boarder of Sichuan, Tibet and Burma. Their religion is a hybrid resulting from this crossroads: Dongba blends Buddhism, Tibetan Bon, Taoism, Confucianism, Mongolian shamanism and local cults.

Part of the reason for Mr. Roosevelt’s success in gathering their art was happenstance. Chinese communists destroyed much of Naxi culture after the Chinese Communist Revolution in 1949, making his loot a time capsule of a thousand-year old culture 10 years before it was nearly extinguished.

Mr. Roosevelt recorded his expedition with a fervor that was part ethnographic, part road trip. Traveling 30 miles a day, sometimes at an altitude of 12,000 feet, with “10 horses, 5 mules, 2 donkeys, 1 goat, 65 soldiers, 10 bodyguards, 3 officials, 12 coolies, 1 interpreter, 1 puppy, myself and three geese,” he ate locusts, grew a beard and slept among rats and lice. He “haggled with local living Buddhas and traded sunglasses, raincoats, compasses and a kitchen stove for ancient sculptures, paintings, scrolls.” Lively drawings of the bandits and soldiers he encountered accompany his notes. He also took lots of photographs.

His journey caused a stir at home: Life magazine covered the trip (“Another Roosevelt to Tibet”), as did various society columns. The five-month expedition was funded by Harvard, with Harvard-Yenching Library and the Library of Congress keeping most of the artifacts he collected.

At the Rubin Museum, 40-foot painted funeral scrolls reveal who the Naxi are and what they care about. Placed at the head of a dead body and unrolled during chanting to guide the deceased to the world of the gods, these “roads of the gods” roll out like film strips of the Naxi spiritual world, taking us through the nine black hills of hell (ruled by yellow and blue frolicking gods and chicken-headed demons) to the 33 gods of heaven.

Naxi art looks like a mash-up of Hieronymus Bosch paintings, Tarot cards and Dante. In one realm of hell, hungry ghosts with seven heads boil people and trample their entrails. (Naxi sins include adultery and, perhaps less predictably Leebu, pretending to be a shaman.) In heaven, things are happier but no less lively: people emerge from eggs, tigers frolic among the seven sacred mountains, and an elephant has sprouted 33 heads.

The Dongba realms are organized according to numerology: valleys and rivers come in the feminine number seven; mountains and trees in the masculine number nine. In this cosmology, every compass point is associated not just with a color but also with a common item: trees, flowers, wombs and eggs.

Naxi tankas, paintings made from ground mineral pigments on cloth that are placed behind an altar, are composed like much Buddhist art: symmetrical and with a large central deity. A god is flanked by its entourage. Its teachers are shown above it, its protectors and offerings below. Most of these gods—often painted in blue, green or gold—are seated cross-legged like Buddhas on a lotus throne.

The Naxi propose a complex world full of smiling animals and monsters: trees adorned with red demons emerge from lotus flowers vomited up by leopard-spotted frogs; tigers and oxen scare ax-wielding monkeys and birds of prey. Animals are sorted into those with hooves, those with claws and those that fly. Along the intricate borders of the paintings, cuckoo birds, dragons, porcupines and elephants abound.

In a pictographic script that looks like a cross between Chinese and hieroglyphics, long manuscripts spell out formulas for things like exorcizing demons. This writing, found nowhere else in the world, may have been modeled on cave paintings; it is mixed with syllabic script in which you can make out the occasional Chinese character.

To the casual viewer, this language flickers on the edge of legibility, yet it contains metaphysical moments: the character representing time shows a growing flower. The manuscripts suggest why and when religion is needed: one ceremony resolves conflicts between two fighting men (this notebook shows two stick people in headdresses, swords crossed); another is for burying young people who commit suicide for love (apparently a widespread Naxi problem). Like the manuscripts, the ceremonial objects in this show attest to religious art’s functional, as well as decorative purposes: a brass bell adorned with a dried eagle claw (a zeba) and a conch shell trumpet (a fvsseimokua) have the patina not just of age but of heavy use. A set of divination cards is worn from years of handling by priests.

Curator Cindy Ho has been planning this exhibition for 16 years. She traveled to Lijiang, the Naxi capital, four times and worked extensively with the Roosevelt family. In a catalogue accompanying the exhibition she writes of her struggle: even among scholars of East Asian Studies, few had heard of the Naxi. The Rubin Museum, which had exhibited the art of the closely related and equally obscure Bon people, was the natural venue for the show.

Leaving China with 20 trunks full of scrolls, manuscripts and skins of exotic animals like golden monkeys, pandas and snow leopards was tricky for Mr. Roosevelt due to the war then being waged between China and Japan; his exit was made possible through a family connection to a certain W. Langhorne Bond, then vice president of the Chinese National Airline; Mr. Roosevelt flew disguised as a steward.

And a good thing, too: shortly after he did so, eccentric botanist-explorer Joseph Rock’s collection of Naxi art and objects was destroyed by Japanese torpedoes as he tried to leave China, leaving Mr. Roosevelt’s collection the largest in the Western world.

After returning with his findings, Mr. Roosevelt led an eventful, if brief, life. After graduation, he enlisted. He was wounded on the Tunisian front, stormed Normandy, won the Purple Heart, Silver Star, and Croix de Guerre, and served in the Office of Strategic Services. He married an American Red Cross worker in England, had three daughters, the oldest of whom was 4 when he died in a plane crash outside of Hong Kong, at just 29 years of age. By then he had taken over the helpful Mr. Bond’s job and was himself the vice-president of the Chinese National Airline.

After 1949, the Chinese communists began more rigorously enforcing the ban on religious activity in remote regions of China. Eventually, the People’s Liberation Army brought stringent reform to mountainous Lijian. Naxi openly practicing the Dongba religion were killed. Tankas and sutras not hidden were destroyed. The area was closed to foreign nationals.

While it’s entertaining to speculate about whether Roosevelt, in seeking out the Naxi, was indeed no more than a youthful scholar, or whether he was sent to the region as a spy, this exhibition proves beyond a shadow of a doubt the lasting effect of his studies. In recent years, elderly Dongba priests, who practiced for 40 or 50 years in secret, have started to emerge, but it is mainly due to the efforts of a 19-year-old kid from Long Island that we know about Naxi art today: because he sought out and preserved their extraordinary art, you can see it at the Rubin Museum.

editorial@observer.com